FR3136058A1 - METHOD FOR MONITORING MOTOR TORQUE OF AN ELECTRIC TRACTION MACHINE - Google Patents

Abstract

The subject of the present invention is a method for monitoring the engine torque of an electric traction machine of an electrified vehicle comprising the determination (22) of a torque difference (EC) between a torque setpoint (CC) and a realized torque (CR) and determining (23) whether the rotor rotates in the forward or reverse direction. According to the invention, the method comprises comparing (24) the torque difference (EC) with respect to a first threshold (S1) in the forward direction and comparing (27) the torque difference ( EC) with respect to a second threshold (S2) in the reverse direction and the activation of a reconfiguration (25, 28) of the electric machine as a function of the result of the comparison (24,27), the second threshold (S2) having a value greater than the first threshold (S1). The invention applies to electrified vehicles with fully electric engines and hybrid engines. Figure 2

Description

METHOD FOR MONITORING MOTOR TORQUE OF AN ELECTRIC TRACTION MACHINE

The field of the invention relates to a method for monitoring the engine torque of an electric traction machine for an electrified vehicle.

In the automotive industry, vehicle manufacturers integrate monitoring functions to ensure the proper functioning of the electric traction machine. In particular, one of these functions consists of permanently monitoring the torque produced by the rotor of the electric machine by measuring it and comparing it to the torque setpoint provided. If too large a deviation is detected, an alert is signaled and the electric machine is reconfigured in a degraded mode.

We know from the state of the art the patent document FR2904108A1 describing a low-cost device for determining the operating characteristics of an electric motor. In particular, it makes it possible to determine the direction of rotation of a motor and variations in speed or operating torque. This device has an advantageous application for vehicle window motors to detect the pinching of an obstacle.

Concerning the electric traction machine, in a desire to optimize its components and its outputs, to extend the lifespan and reduce its cost, we sought to optimize the electric machine with regard to the requirements in torque accuracy in the forward direction of the vehicle relative to the reverse direction. Therefore, the precision of the torque produced by the rotor of the traction machine in forward motion is higher than that of the torque produced in reverse.

There is a need to improve the torque monitoring function produced by an electric traction machine in order to guarantee the best performance and to increase the level of requirements for torque control. An objective of the invention is also to improve fault diagnostics and to avoid untimely alerts and reconfigurations of the electric traction machine of a motor vehicle. Another objective is to offer an electric machine at a lower cost while improving the requirements in terms of operational safety.

More specifically, the invention relates to a method for monitoring the motor torque of an electric traction machine of an electrified vehicle comprising the determination of a torque difference between a torque setpoint transmitted to the electric machine and a torque produced by the rotor of the electric machine and determining whether the rotor rotates in the forward direction of the vehicle or the reverse direction of the vehicle. According to the invention, the method comprises comparing the torque difference with respect to a first threshold when the rotor rotates in the forward direction and comparing the torque difference with respect to a second threshold when the rotor turns in the reverse direction and activates a reconfiguration of the electric machine according to the result of the comparison. The second threshold has a torque value greater than the first threshold, thereby reducing the design requirements for reversing and reducing the cost of the electric machine.

According to a variant, the method further comprises controlling a first reconfiguration of the electrical machine if the deviation is greater than the first threshold in the forward direction for at least a first duration.

According to one variant, the first duration is equal to 450 milliseconds.

According to a variant of the first reconfiguration, the method includes memorizing a first fault code in a first state, reporting a fault and stopping the electrical machine. The first state is a so-called permanent state.

According to a variant, the method further comprises controlling a second reconfiguration of the electric machine if the deviation is greater than the second threshold in the reverse direction for at least a second duration.

According to one variant, the second duration is equal to 100 milliseconds.

According to a variant of the second reconfiguration, the method includes memorizing a second fault code in the first state, reporting a fault and stopping the electrical machine. The first state is a so-called permanent state.

According to a variant, the method further comprises, in the event of activation of the first reconfiguration or the second reconfiguration and in the event of detection of a vehicle shutdown command, the command of a rehabilitation of the operation of the machine electrical, stopping the reporting and storing the first or second fault code in a second state. The second state is a so-called fugitive state.

According to a variant, the first threshold is equal to 50 N.m and the second threshold is equal to 60 N.m

It is further envisaged an electrified vehicle comprising an electric traction machine and a control unit of the electric traction machine in which the control unit is configured to implement the monitoring method according to any of the modes of previous achievements.

We further envisage a computer program product comprising instructions which, when the program is executed by a computer of the electric traction machine, lead it to implement any one of the embodiments of the monitoring method of the motor torque according to the invention.

The use of two torque monitoring thresholds of distinct values, differentiating forward and reverse of the electric machine, makes it possible to optimize the design of the electric machine in the direction of rotation of the machine which corresponds to walking front of the VHL. This monitoring method makes it possible to reduce the costs of the electric machine, due to reduced design requirements in the reverse direction.

Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows including embodiments of the invention given by way of non-limiting examples and illustrated by the appended drawings, in which:

schematically represents a powertrain of an electrified motor vehicle configured to implement the method according to the invention.

represents a preferred embodiment of the monitoring method according to the invention.

The invention applies to electrified vehicles, in particular motor vehicles with 100% electric engines and hybrid vehicles. The invention relates more precisely to a method for monitoring the torque of the electric traction machine of an electrified vehicle.

In , there is schematically represented an example of a powertrain of an electrified vehicle 1 intended to implement the invention. The powertrain 1 comprises a control unit 16, designated by the acronym eVCU for “Electric Vehicle Control Unit” in English, supervisor or the acronym ECU for “Electronic Control Unit”, an electric traction machine 10 powered by a system traction battery 14, and a traction chain of a motor torque CR transmitted by the rotor of the electric machine 10 to the wheels of the vehicle.

Conventionally for a 100% electric traction vehicle, the traction chain includes in particular a reduction gear 11 mechanically connected in rotation to the rotor and a mechanical transmission 12 of the engine torque to each traction wheel of the vehicle. Other transmission architectures are possible for the monitoring method according to the invention, in particular for hybrid architectures.

Furthermore, it is intended, but not shown on the , an on-board charger for the battery system 14, a charging socket box intended to connect the vehicle to an external electrical power source, for example a domestic socket, domestic fixed station (commonly called "Wallbox" in English), a charging station at a motorway station provided for this purpose, or even a mobile charging station.

The traction battery system 14 is intended for the electrical supply of the traction machine 10 of the vehicle. It comprises electrical energy storage means 142. In the context of the invention, the voltage of the traction battery system 14 can be of the 48V type or higher, of the 400 volt type according to the preferred embodiment (between 350 volts and 450 volts), 800 volts type (between 700 volts and 900 volts), or even more. The battery 142 comprises energy storage elements comprising electrochemical cells, for example of the Lithium-ion type.

The battery system 14 also includes a management computer 141 (designated by the acronym BMS for “Battery Management System” or TBCU for “Traction Battery Control Unit”) adapted to supervise the parameters specific to the battery 142 in cooperation with sensors current and voltage, such as the state of charge SOC (“State of Charge”), the open circuit voltage OCV (“Open Circuit Voltage”) expressed in Volts, the charging current expressed in Amperes, the state of health SOH (“State of Health), the voltage or even the temperature of the battery 142.

Furthermore, the supervision control unit 16 supervises the electric traction machine 10, the traction battery system 14, in particular. The control unit 16 has the function of centralizing the data collected from the vehicle and retransmitting them to other vehicle computers via a data communication bus 15, for example of the CAN type.

More precisely, the supervision computer 16 permanently determines the torque setpoint to be produced at the wheels and the CC torque setpoint to be produced by the electric machine 10 at the rotor output. For example, the CC torque setpoint can be determined from the torque setpoint at the wheels and the value of the reduction of the gearbox 11. The CC torque setpoint to be produced is transmitted through the communication bus 15 to the electric machine traction 10.

The computer 16 includes, recorded in memory, a map 161 delivering a set torque value to the wheel according to the following parameters 162: the direction of travel of the vehicle forward/rear from a gear lever sensor, depressing the accelerator and brake pedal ENF and the vehicle speed VIT, received for example from a trajectory control computer.

More precisely, the electric traction machine 10 comprises a computer 13 with integrated circuits, of the microprocessor type and with memories, configured for controlling the electric machine 10, designated by the term MCU for “Machine Control Unit” in English. The electric traction machine 10 is in this example a permanent magnet synchronous machine. The computer 13 develops and transmits a current setpoint to an electrical converter. The current setpoint is determined from a correspondence map recorded in the memory of the computer 13 delivering the necessary quantity of current that the converter must draw from the high voltage electrical network in response to the requested torque setpoint, as a function of the voltage of the high voltage network and the temperature of the stator of the electric traction machine 10. This converter draws current from the voltage network supplied by the battery system 14 to power the poles of the stator of the electric traction machine 10.

In particular, the computer 13 comprises a monitoring module 131 whose function is to implement the engine torque monitoring method according to the invention. For its execution, the module 131 permanently determines the torque produced CR during its operation. In a manner known per se, the torque produced CR is determined from the mechanical power Pm supplied to the transmission chain by the rotor according to the relationship Pm=Cr*W, which power Pm can be calculated from the electrical power Pe in input of the electric machine 10 and a predetermined efficiency coefficient Rd of the electric machine 10. And, W is the instantaneous rotation speed of the rotor, expressed for example in rpm.

In particular, the efficiency coefficient Rd is measured on the bench for each speed step, torque step, for each voltage step, for each supply current step and for each stator temperature step. A map of the Rd values is learned on the bench and is recorded in the memory of the computer 13 so that the latter can determine the coefficient Rd at any time during the operation of the electrical machine 10.

Furthermore, the computer 13 is capable of permanently determining during its operation, by measurement or reception, the following operating parameters: the voltage U at the terminals of the electrical machine 10, the current drawn I by the electrical machine 10, the rotation speed W of the rotor and the temperature of the stator.

Thus, the monitoring module 131 constantly calculates the torque produced CR according to the following formula and the recorded efficiency map: CR=U*I*Rd/W

In addition, the monitoring module 131 continuously determines the CC torque setpoint during its operation. The CC torque reference is received by the computer 13 through the communication bus 15.

In addition, the monitoring module 131 permanently determines the difference EC between the torque achieved and the torque setpoint CC according to the following formula: EC=abs(CR-CC), where abs() is the absolute value function. The monitoring module 131 is configured in memory by at least two torque thresholds S1 and S2, and two predetermined durations D1 and D2, S1 and D1 corresponding specifically to forward torque monitoring, and S2 and D2 specifically to monitoring backwards. S1 is an acceptability criterion for torque difference in forward gear and S2 is an acceptability criterion for torque difference in reverse gear. S2 is greater than S1 in torque value because a greater torque difference is allowed in reverse. D1 and D2 are the maximum acceptable durations of an EC deviation when this deviation is greater than S1 or S2. D1 and D2 have distinct values.

In addition, the monitoring module 131 is capable of activating a reconfiguration of the electrical machine 10 in the event of detection of a torque anomaly in forward or reverse gear. The reconfiguration consists of controlling a degraded mode of the electrical machine. For example, reconfiguration imposes a maximum torque limit or prevents torque delivery altogether. According to the invention, at least two reconfiguration modes are provided, a first forward mode and a second reverse mode. Furthermore, each reconfiguration mode can be deactivated according to deactivation conditions specific to each mode. Examples of conditions will be described in .

Furthermore, for the purposes of the monitoring process, the control unit 16 collects information relating to anomalies detected by the electric traction machine 10 so as to retransmit it to another centralized control unit (not shown in ) designated by the acronym BSI for Intelligent Service Box. In this non-limiting example, the BSI box and the control unit 16 communicate via a second communication bus, of the CAN type. More precisely, the BSI box is responsible for recording a diagnostics and alerts log that can be consulted by after-sales services. An anomaly is recorded in the memory of the BSI box in the form of an anomaly code representing the level of severity and the state of the anomaly. An anomaly can be recorded in a permanent state (i.e. the anomaly is still in progress) or in a fleeting state (the anomaly is no longer detected but the event remains recorded in the history from Journal).

In , a diagram representing a preferred embodiment of the algorithm of the method for monitoring the motor torque of an electric traction machine for an electrified vehicle according to the invention is described. In reference to the , the method is implemented by the monitoring module 131, in this example the computer 13 of the electrical machine 10. But this is not obligatory, the monitoring module 131 could be external to the computer 13, while being coupled to the latter 13. In the latter case, it can itself be arranged in the form of a dedicated computer comprising a possible dedicated program, for example. Consequently, the monitoring module, according to the invention, can be produced in the form of software (or computer (or even “software”)) modules, or of electronic circuits (or “hardware”), or even of a combination of electronic circuits and software modules.

In an initial step 21, the vehicle is started and the electric machine is put into operation. The gear lever is for example in the forward position or in the reverse position. The driver presses the brake pedal or the accelerator pedal. The vehicle is moving at a given speed VIT.

In a second step 22, the monitoring module 131 calculates the difference EC between the torque produced CR and the torque setpoint CC. The torque setpoint CC and the torque achieved CR are determined by the monitoring module 131 in accordance with the description of the .

In a third step 23, the monitoring module determines the direction of travel of the vehicle AV/RE so as to select the threshold value specific to the direction of travel from among the values S1 and S2 recorded in the memory of the monitoring module. The direction of travel is preferably determined from the information delivered by a piezometric sensor of the electric traction machine making it possible to detect the direction of rotation of the rotor.

In a fourth step 24, the monitoring module compares the deviation EC with the value S1 if the rotor of the electric machine rotates in the positive torque direction of forward travel AV. In addition, if the EC deviation is greater than S1, the monitoring module checks whether this EC deviation remains greater than S1 for a duration D greater than the duration D1. In this non-limiting example, S1 is equal to 50 N.m and D1 is equal to 450 milliseconds. D1 can be equal to lower or higher values.

In a fifth step 25, if EC is greater than S1 for a duration D greater than the duration D1, the monitoring module activates a first reconfiguration mode MR1 of the electric traction machine. The first MR1 reconfiguration mode consists of stopping the electric traction machine (the supply of torque is prevented), recording a fault code in non-volatile memory, also called read-only memory or reprogrammable read-only memory (ROM ("Read"). -Only Memory" in English) or EPROM ("Erasable Programmable Read-Only Memory")) and to communicate this fault code to the vehicle's eVCU control unit for diagnostic purposes. This fault code is representative of an anomaly of non-compliance with the torque setpoint of the electric machine in forward gear. Furthermore, the electric machine's computer requires a “stop” light to be turned on on the dashboard and a message informing vehicle users that a problem has occurred with the traction chain. The fault code is recorded in a so-called permanent state, indicating that the anomaly is present.

This first reconfiguration mode MR1 can be deactivated in a sixth deactivation step 26 when a first deactivation condition is detected. Failure to comply with the forward torque instruction is considered a critical anomaly. Therefore, the first condition for deactivation is the intervention of a technical service on the electric machine, including checking the diagnostic log and erasing the non-volatile memory of the electric machine computer. Once the intervention is executed, the process returns to initial step 20 and returns to a verification loop.

Furthermore, in step 24, as long as the deviation EC remains less than the threshold S1 or is greater than S1 for a duration D less than D1, the process returns to initial step 20 and returns to a verification loop.

Returning to step 23, in the event of detection of a reverse reverse gear, in a seventh step 27, the monitoring module compares the deviation EC with the value S2. The rotor of the electric machine turns in the negative direction in reverse reverse torque. In addition, if the EC deviation is greater than S2, the monitoring module checks whether this EC deviation remains greater than S2 for a duration D greater than the duration D2. In this non-limiting example, S2 is equal to 60 N.m and D2 is equal to 100 milliseconds. S2 is necessarily greater than S1. D2 can be equal to lower or higher values.

In an eighth step 28, if EC is greater than S2 for a duration D greater than the duration D2, the monitoring module activates a second reconfiguration mode MR2 of the electrical machine. The second MR2 reconfiguration mode consists of stopping the electrical machine (the supply of torque is prevented), recording a fault code in non-volatile memory, and communicating this fault code to the vehicle's eVCU control unit. for diagnostic purposes. This fault code is representative of an anomaly of non-compliance with the torque setpoint of the electric machine in reverse. Furthermore, the electric machine's computer requires a “stop” light to be turned on on the dashboard and a message informing vehicle users that a problem has occurred with the traction chain. The fault code is recorded in a so-called permanent state, indicating that the anomaly is present. In this preferred embodiment, mode MR2 differs from mode MR1 by its deactivation condition 29.

More precisely, the second reconfiguration mode MR2 can be deactivated at a ninth deactivation step 29 when a second deactivation condition is detected. Failure to comply with the torque instruction in reverse is considered less critical than in forward gear. Consequently, the second deactivation condition is detection of the vehicle extinction event, also called “ignition cutoff” of the vehicle by actuation of a key or vehicle off/on button.

This condition called “contact cutoff” authorizes exit from MR2 reconfiguration mode. The process then returns to initial step 20 and the vehicle is authorized to leave again. In this case, the computer of the electrical machine controls a rehabilitation 30 of the electrical machine consisting of controlling the stopping of the lighting of the “stop” indicator light and the anomaly message, of authorizing the operation of the electrical machine and to record in the non-volatile memory of the computer and the eVCU control unit the fault code in a second state called fugitive state for diagnostic purposes. The fugitive state indicates that the anomaly no longer exists and has the function of recording the event for later analysis. At initial step 20, the process returns to a verification loop.

However, we envisage as a variant that the second deactivation condition 29 is the intervention of a technical service, identical to the first condition 26. The fault code remains in a permanent state and the electric traction machine remains stopped until technical intervention.

As an optional variant, in order not to immobilize the vehicle even in the event of a fault detected in forward mode, it is envisaged, in step 26, that a detection of a vehicle extinction control event, called "contact cut-off" , authorizes exit from MR1 reconfiguration mode. The process then returns to initial step 20 and the vehicle is authorized to leave again. This variant, not shown in , includes a step of rehabilitation of the traction machine identical to step 30 before returning to initial step 20.

Claims (10)

Method for monitoring the motor torque of an electric traction machine (10) of an electrified vehicle comprising the determination (22) of a torque difference (EC) between a torque setpoint (CC) transmitted to the electric machine and a torque produced (CR) by the rotor of the electric machine (10) and the determination (23) whether the rotor rotates in the forward direction of the vehicle or the reverse direction of the vehicle, characterized in that it comprises comparing (24) the torque difference (EC) with respect to a first threshold (S1) when the rotor rotates in the forward direction and comparing (27) the torque difference (EC) with respect to at a second threshold (S2) when the rotor turns in the reverse direction and the activation of a reconfiguration (25, 28) of the electric machine (10) according to the result of the comparison (24,27), the second threshold (S2) having a value greater than the first threshold (S1). Monitoring method according to claim 1, characterized in that it further comprises the control of a first reconfiguration (25) of the electrical machine (10) if the deviation (EC) is greater than the first threshold (S1) in the forward direction (AV) for at least a first duration (D1). Monitoring method according to claim 2, characterized in that the first duration (D1) is equal to 450 milliseconds. Monitoring method according to claim 2 or 3, characterized in that the first reconfiguration (25) comprises the memorization of a first fault code in a first state, the signaling of a fault and the stopping of the electrical machine (10 ). Monitoring method according to any one of claims 1 to 4, characterized in that it further comprises the control of a second reconfiguration (28) of the electrical machine (10) if the deviation (EC) is greater than the second threshold (S2) in the reverse direction (AR) for at least a second duration (D2). Monitoring method according to claim 5, characterized in that the second duration (D2) is equal to 100 milliseconds. Monitoring method according to claim 5 or 6, characterized in that the second reconfiguration (28) comprises the memorization of a second fault code in the first state, the signaling of a fault and the stopping of the electrical machine. Monitoring method according to any one of claims 2 to 7, characterized in that it further comprises, in the event of activation of the first reconfiguration (25) or the second reconfiguration (28) and in the event of detection of 'a command to turn off the vehicle, the command to rehabilitate (30) the operation of the electrical machine (10), stop the reporting and memorize the first or second fault code in a second state. Monitoring method according to any one of claims 1 to 8, characterized in that the first threshold (S1) is equal to 50 N.m and the second threshold (S2) is equal to 60 N.m Electrified vehicle comprising an electric traction machine (10) and a control unit (13) of the electric traction machine (10), characterized in that the control unit (13) is configured to implement the monitoring method according to any one of claims 1 to 9.